Optical networks for transmitting optical data signals are known from the literature. In principle, a basic distinction is made between access networks and transport networks for the transmission of data. The access networks, which ensure access to the consumer are characterised by complex network structures. The variety of systems of these predominantly service-specific access systems is very wide. Within a communications network the access network has the task of providing the subscribers with access to switching equipment, for example servers. From its location, each subscriber first has to be connected to a supply node so that it can actually take advantage of the services on offer. Generally, all communication means are suitable for the subscriber connection. In the long-distance network the telecommunication traffic is concentrated in point-to-point circuits between the various network nodes and switching nodes. On the other hand, in the access network very different requirements have to be met. Standardised functions (BORSCHT) have to be implemented for the technical interaction between the subscriber exchanges and the local ends. The subscribers themselves are not distributed homogeneously over the entire access area, rather there are local areas with high subscriber densities but also areas in which the subscribers occur sparsely. Depending on the respective communications requirement, a distinction can be made between very different subscriber groups such as private customers and smaller or larger business customers to whom suitable transmission solutions have to be offered. The access networks in particular require a large capital investment on the part of the network operator. The components are exposed to environmental effects and in every case have to be individually available to the subscribers of the access network.
The network structure according to the invention, which takes account of the above-mentioned observations, is introduced in order to improve the economy of access networks.
The proposed optical network has the advantage that simple components are employed in the access area. In addition, due to the combination of different transmission methods, a high degree of flexibility is provided for modifications in the access area. The costs of translating from one transmission method to another transmission method are reduced by the use of new types of converters. The optical network according to the invention combines in the access area a time-division multiplex method in one network layer with a code-division multiplex method in a second network layer. Furthermore, the optical network is expanded to a wavelength-division multiplex method at the inner city level. The connection from the subscribers to the central switching centre is made in the entire network and is exclusively optical. The connection to a transport network is only made from the last network layer, the wavelength-division multiplex network layer, whereby the incoming optical signals are received, electrically regenerated and converted in accordance with the requirements of the transport network.
Advantageous developments and improvements of the optical network stated in the main claim can be achieved by means of the measures listed in the sub-claims.
The use of a special converter for the conversion of time-division multiplex signals to code-division multiplex signals is particularly advantageous. This converter represents a cost-effective solution to realise a conversion from time-division multiplex to code-division multiplex signals. In this case the conversion is effected exclusively along optical paths.